The World Health Organization has cast doubt on China's decision to kill thousands of animals it believes may be responsible for the emergence of one case of Severe Acute Respiratory Syndrome, known as SARS, in the southern province of Guangdong.

The spokesman for the World Health Organization, Iain Simpson, says there is no conclusive evidence linking the animal, the civet cat, to the SARS outbreak.

"We believe that more research is needed, and we also believe that if the cull [killing] is to be carried out, it is essential that it be carried out in a very controlled way, because otherwise there is a risk of both human and environmental contamination," he said. "Again, explicitly, the people who are carrying out the slaughter are at risk of infection, and there is also a risk of environmental infection."

Mr. Simpson says a thorough risk assessment should be done before any mass killing of civet cats.

Civet cat is a term applied to several types of mongoose. They are only distantly related to ordinary household cats, and are not felines at all. Civet cats are hunted or raised as food, and they are considered a delicacy in parts of Asia and Africa.

The type of SARS found in civet cats is almost identical to the type that affects humans. But the WHO is concerned that focusing entirely on the animals might divert attention from other possible causes for the re-emergence the deadly disease, which killed more than 700 people around the world last year. The U.N. agency is also concerned that any crackdown on street markets where civet cats are sold would drive the trade to secret locations, where it would be impossible to monitor or control.

WHO spokesman Iain Simpson said it is not even clear whether the man who has SARS in southern China actually got the disease from a civet cat. "One of the things that we are trying very hard to do is to understand how this man became infected," said Mr. Simpson.

"That is not at all clear," he continued. "So, that is the big question, and once we have answered that, then we will know a lot more about this individual case. Again, it is an individual case, and there are no others currently confirmed anywhere."

Mr. Simpson said that includes people who were in contact with the infected man, a 32-year-old television producer.